A floor jack uses pressurised fluid to cause the jack's lift surface to rise. Over time, air can enter the jack's fluid reservoir, particularly if the jack's seals are not functioning properly. Operating a jack with air in its system is dangerous, as the air within the reservoir can lead to sudden failure of the jack, particularly when the jack is supporting a heavy load. The most common symptom of air in the floor jack is a spongy feel when the jack is used. Also indicative of the presence of air is a jack that slowly lowers itself. When either occurs, it is time to bleed the air from the jack.
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Things you need
- Flathead screwdriver
- Jack's user's manual
Jack the jack up until the jack's ram piston is fully extended. The ram piston is the portion of the jack which rests just below the object to be lifted.
Release the pressure valve and allow the jack to lower itself. The pressure valve is typically located on the side of the jack and can be released with a flathead screwdriver. To release the valve, turn the valve in a counterclockwise direction with the screwdriver.
Open the jack's filler plug. The filler plug is generally located on the main body of the jack. The filler plug should not be confused with the two check valves, which look very similar and should not be disturbed. It is therefore imperative to check the jack's user's manual to identify the precise location of the filler plug. The filler plug can be opened by turning it in a counterclockwise direction with a flathead screwdriver. When the plug is removed, a short hissing sound indicates that the air trapped inside the jack has escaped.
Reinsert the filler plug into the jack.
Repeat the above steps until air can no longer be heard escaping from the jack to complete the bleeding process.